Thus, the contribution of a neutral scalar \(S\)  to the triangle one-loop diagram of \(g-2\)  is [1]}
\(\Delta a_{\ell }\ = \ \frac{|y_{i j}|^{2}}{8\pi ^{2}}\frac{m_{\ell }^{2}}{m_{S}^{2}}\int _{0}^{1}{\rm d}x\frac{x^{2}(1-x \pm \epsilon _{l_i})}{(1-x)(1-x\epsilon _{S}^{2})+x\epsilon _{l_j}^{2}\epsilon _{S}^{2}}\,,\) 
